macviews: fix UserManager::IsShowing

This method did the wrong thing in Mac Views mode. Fixing it
fixes most of the AppControllerNewProfileManagementBrowserTest
suite.

Bug: 834754
Change-Id: I9e2971b4e5d3cff12a1629f70c96a5cb65e40aa1
Reviewed-on: https://chromium-review.googlesource.com/1020021Reviewed-by: Sidney San Martín <sdy@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#552125}

chrome/browser/ui/views/profiles/user_manager_view.cc

@@ -194,6 +194,13 @@ bool UserManager::IsShowing() {
 #if defined(OS_MACOSX)
   if (views_mode_controller::IsViewsBrowserCocoa()) {
     return UserManager::IsShowingCocoa();
+  } else {
+    // Widget activation works differently on Mac: the UserManager is a child
+    // widget, so it is not active in the IsActive() sense even when showing
+    // and interactable. Test for IsVisible instead - this is what the Cocoa
+    // UserManager::IsShowing() does as well.
+    return g_user_manager_view ? g_user_manager_view->GetWidget()->IsVisible()
+                               : false;
   }
 #endif